肌肉質量的多寡會影響肌肉的耐受度與疲勞的產生，而肌肉質量會隨者年齡的增長而逐漸下降，其中下肢肌肉質量的流失，會使下肢更易疲勞、平衡能力下降、步態不穩定性上升造成跌倒風險增加。於工業安全與長者安全上，將是現代社會不容忽視的問題。而對於動態平衡與步行移動之下肢肌群中，以小腿後側腓腸肌最為重要。本研究針對雙側腓腸肌疲勞前後，搭配表面肌電訊號之中位頻率變化確認疲勞狀態，並透過慣性感測元件（Inertial Measurement Unit, IMU）蒐集身體6個部位於步態中的之加速度與角速度等資訊特徵。使用深度學習技術辨識下肢肌肉疲勞之步態，找出對於疲勞步態辨識最為準確之部位。期許未來能進一步應用至工業或醫療場域中，將有助於提升工業和日常生活的安全性。
本研究之對象為16名年齡範圍20至30歲之健康成年人，男性與女性各8名。將IMU黏貼於雙腳腳跟與腳趾、薦椎、頭部共6個部位後，請受試者於70公尺的走廊行走。實驗分二日進行，間隔七日。首日受試者分別於下肢疲勞誘發前後於長廊進行自覺舒適速度之步態及疲勞步態測試。第二日則請受使者以首日疲勞後之步頻行走，以模擬疲勞後之步態，幫助確認肌肉疲勞對於步態的影響。研究結果顯示，透過IMU進行步態的辨識，於疲勞前、疲勞後即模擬步頻三種情況下；模擬步頻之辨識準確率於各IMU組合下，皆高於另二種情況，顯示腓腸肌的疲勞對於步態模式的影響確實對於非疲勞時的情況下有明顯的差異。於步態三種情況下之辨識準確度，身體各部位中辨識準確度以腳趾最高，頭部為最低；而於各IMU組合之下，腳趾與薦椎的搭配之下有最高之辨識準確度，顯示薦椎與足部的相互變化對於步態的辨識有較佳的學習效果。
本研究之結果可以得知，使用深度學習技術LSTM及透過單一部位之IMU即可辨識此步態是屬於何種狀態。一般正常生理狀態，或是小腿肌肉疲勞狀態，亦或是模擬疲勞步頻下，肌肉未疲勞的狀態。未來研究中將加入更多不同年齡層之受試者，及搭配不同活動的疲勞步態，幫助增加未來應用上之可行性，並讓能應用之場所更加多元。

Sarcopenia is a type of muscle mass loss that occurs with aging. The amount of muscle mass affects the tolerance of a muscle towards fatigue. Muscle mass loss and fatigue, especially in lower limbs, induce walking imbalance and gait instability, increasing the risk of falling. Lower limb muscles, such as gastrocnemius muscles, are important for human locomotion and daily activities. The study aims to use a deep learning technique to recognize the data collecting from inertial measurement units (IMUs) for fatigued gait. Second, the study aims to reveal the location or the number of IMUs can have the best performance.
Sixteen healthy adults (24.4 ± 2.07) participated in the experiment. Six IMUs were attached to each subject’s heels, toes, sacrum, and head. The research is a two-day process with a week interval. On the first day, the subjects were instructed to walk along a hallway before and after the fatigue protocol as a non-fatigued and fatigue gait. On the second day, the subjects were instructed to walk along a hallway following the beat of their fatigue gait cadence measured on the first day. The result revealed that the LSTM model could recognize the gait of simulated cadence with the highest accuracy among these three conditions (non-fatigued, fatigue, and simulated cadence). For the IMU location, the result showed that the IMUs attached to the toes had the highest accuracy. For multiple IMUs combinations, the result showed that the IMUs of toes and sacrum achieved the highest accuracy among other combinations.
In conclusion, the deep learning technique of LSTM with one or more IMUs can recognize the gait under normal, physical fatigue, or simulated cadence without muscle fatigue. For future researches and applications, more subjects from different ages would be expected to collect and along with other walking conditions to improve the feasibility in multiple fields such as industrial and elderly safety.

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